The instant invention relates to a new method for processing parts using solvents. More particularly the present invention relates to a single chamber solvent processing method whereby parts that require solvent processing can be subjected to multiple processing steps in one containment chamber.
In the finishing of metals, plastics, ceramics, composites and other materials, often many process steps are required either for intermediate processing or to produce a finished product. Some steps may include cleaning, drying, anodizing, film deposition, painting, impregnating, curing, heat-treating and other processes. Most of these steps require the use of organic solvents and/or inorganic chemicals, which often are regarded as environmental hazards, or health threats to workers. As a result, more often than not these processes are highly regulated by the EPA and/or local air and water pollution agencies. Quite often, these processes are carried out in special areas to either control emissions or limit ambient contamination between process steps. For these types of processes, it would seem advantageous to be able to perform multiple steps within a single chamber or enclosed environment in order to maintain the required quality control and/or limited emissions to the work place. Such a process method would improve the product quality and reduce pollution, labor costs and overall costs of controlled environment work areas such as clean rooms.
In this regard, the present invention is directed to a controlled environment processing chamber or chambers in which solvents and/or solutions used for processing a material can be introduced. The process includes a means of applying a negative gauge pressure to the chamber to remove air or other non-condensable gases. Means are provided for introducing a solvent, solvent mixture or solution in either a liquid or vapor state. A first system recovers solvent(s) or solution(s) from the object being processed and chamber, and a second system, separate from the first system, further recovers residual solvent or solution from the object and chamber. Treatment may be in the form of coating, etching, deposition, cleaning, stripping, plating, adhesion, dissolving, penetrating, anodizing, impregnating, de-binding or any other process in which material is removed or deposited on a solid surface by transfer from or to a liquid or gas phase.
In another aspect of the invention, a method of processing an object in an enclosed solvent processing system, including a solvent supply system in sealable communication with a cleaning chamber comprises the steps of:
(a) sealing the solvent or solution supply system with respect to the chamber;
(b) evacuating the supply system of air and non condensable gases and maintaining this air free environment
(c) opening the chamber to atmosphere and placing an object to be processed in the chamber;
(d) evacuating the chamber to remove air and other non-condensable gases;
(e) sealing the chamber with respect to atmosphere;
(f) opening the chamber with respect to the solvent supply system and introducing a solvent or solution into the evacuated chamber;
(g) processing the object while maintaining an air free environment within the chamber;
(h) recovering and processing the solvent or solution introduced into the chamber within the closed circuit processing system;
(i) introducing another solvent or solution as a liquid, gas or vapor to further process the object;
(j) recovering and processing the 2nd solvent or solution introduced into the chamber within the closed circuit processing system;
(k) repeating steps (h) and (i) as required;
(l) sealing the chamber with respect to the solvent supply system closed circuit solvent processing system;
(m) introducing air or other non condensable gases into the chamber for sweeping further solvent on the object and within the chamber; and
(n) opening the chamber and removing the treated object.
The main objective of this invention is to maintain two or more solutions used for processing an object in two or more steps at a relatively constant concentration state from batch to batch. In order to accomplish this, a process must either prevent any mixing of solvent or solution vapors or liquids with previous solvents or solutions used in the processing, or separate solvents mixed during different processing steps to return the solutions to their starting compositions. Another main objective of this invention is to prevent solvents or solutions used in the processing from mixing with air, which would eventually lead to this solvent escaping the system as this air is discharged during the process. Any air used for solvent recovery, motive gas for vacuum, drying, curing, or other processing is internally circulated to provide a closed looped system requiring no discharge of air or solvent from the unit.
Another object of this invention is to provide an improved closed circuit solvent system and method, which enables solvent recovery and limits hazardous emissions. The invention can employ a variety of solvents having boiling points as low as 70 degrees Fahrenheit and as high as 500 degrees Fahrenheit.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.